Solutions of hydroxylamine are inherently unstable, decomposing by internal oxidation-reduction to form ammonia and nitrogen or nitrogen oxides. The decomposition is accelerated by high pH and the presence of catalytic amounts of cations such as Fe(II), Ni(II), and Cu(II). Aqueous solutions thereof are commonly produced by at least the partial neutralization of the hydroxylamine salt, such as the hydrochloride or sulfate, with an alkali metal hydroxide or ammonia. These solutions are widely used in synthesis work, but the instability of the free hydroxylamine in these solutions limits its utility in cases where storage is necessary.
There have been a number of attempts reported to stabilize solutions of an hydroxylamine or an at least partially neutralized hydroxylamine salt in order to achieve a longer shelf life. Compounds that have been reported to be stabilizers for such solutions include various chelating agents (such as the tetrasodium salt of ethylene diaminetetraacetic acid) (U.S. Pat. No. 3145082); amide oximes (U.S. Pat. No. 3480391); hydroxamic acids (U.S. Pat. No. 3480392); hydroxyureas and hydroxythioureas (U.S. Pat. No. 3544270); hydroxylalkylidene diphosphonic acids (U.S. Pat. No. 3647449); vicinal polyhydroxyphenols (Japanese Patent No. 48/78099); hydroxyquinolines (Japanese Patent No. 57/100908); 1,10-phenantholine (Japanese Patent No. 58/69841); dipyridyl compounds (Japanese Patent No. 58/69842); thiocarboxylic acids (Japanese Patent No. 58/69843); quinoline derivatives (Japanese Patent No. 58/69844); hydroxy substituted flavone (German Patent No. 3343597); anthocyanins (U.S. Pat. No. (4551318); hydroxyl substituted flavan (German Patent No. 3343599); stannic acid (Japanese Patent No. 60/260541); hydroxy substituted anthraquinones (U.S. Pat. No. 4576804); 8-hydroxyquinalidines (U.S. Pat. No. 4629613); and 2,3-dihydrohexano-1,4-lactone (U.S. Pat. No. 4634584).